Artificial nail compositions are described in U.S. Pat. No. 4,104,333, granted Nov. 15, 1977, and assigned to Lee Pharmaceuticals. In these compositions, the curable binder is a combination of at least two monomers, one of which is a monofunctional acrylate, preferably either tetrahydrofurfuryl acrylate or tetrahydrofurfuryl methacrylate, and the other of which is a polyfunctional carboxylate.
Formulating such an artificial nail coating composition is very challenging. The composition must be curable, once mixed, within a time period that is acceptable to the consumer. As a practical matter this means that curing must occur within about 120 to about 400 seconds after mixing and application. In addition, for greatest convenience and acceptability, curing must occur under ambient conditions to which the nail is normally exposed including ambient temperature and normal atmospheric conditions.
When cured, the coating must have sufficient adhesion to the substrate nail to resist mechanical removal. It must be strong and hard, like the natural nail. At the same time, it must be sufficiently flexible so that it can withstand the normal stresses to which human nails are ordinarily subjected, without cracking or breaking, and it must be removable at will in a reasonably convenient way.
Formulating a nail coating composition or artificial nail composition that has all of these characteristics, especially freedom from brittleness, is very difficult. In U.S. Pat. No. 4,104,333, certain dibenzoates and phthalates or diphthalates are suggested for use as flexiblizers. Such components add to the cost of the formulation, and while imparting a certain degree of flexibility, dilute the binder and filler, and thus require an added degree of formulating skill to balance the proportions of the ingredients in order to obtain the desired physical characteristics in the cured article.